Glynn Clements wrote:
> Bug Hunter wrote:
>
> > we opened a pipe without error. we then did this:
> > FD_ZERO(&InputFD); // initialize read descriptors
> >
> > FD_SET(s,&InputFD); // Add socket to descriptors to
> > FD_SET(FromDH,&InputFD); // wait on Modem data as well
> >
> > FD_ZERO(&wErrorFD);
> > FD_SET(s,&wErrorFD);
> > FD_SET(FromDH, &wErrorFD);
> >
> > signal(SIGALRM,SignalHandler);
> >
> > while(1){
> > wInputFD = InputFD;
> > // don't wait more than 500msec before reporting
> > timeout.tv_sec = 0;
> > timeout.tv_usec = 500000;
> > short result =
>select(FD_SETSIZE,&wInputFD,NULL,&wErrorFD,&timeout);
> > ...
> >
> >
> > We get a 2 from select, then the pipe (FromDH) indicates
> > an error. errno is zero. There is no error that we can
> > see. any clues?
>
> What do you mean that the pipe `indicates an error'?
>
> Note that the third fd_set (fourth argument to select) indicates
> `exceptional conditions', not necessarily errors.
>
> Also, errno is only set if some library function indicates an error
> (usually by returning -1, NULL, etc). If select() returns 2, then it
> won't have set errno.
>
Im sorry, I phrased that badly. wErrorFD indicates an exception for the pipe:
if (FD_ISSET(FromDH,&wErrorFD) )
{
/* error */
}
This always takes the error for the pipe. I don't get this for the other handles.
Is
there something special about pipes that indicate an exception??
When we opened the pipe, there were no problems. We opened the pipe like this:
FromDH=open(FROMDH_PIPE,O_RDONLY | O_NONBLOCK);
if(FromDH<0){
printf("Error in %s at %d =>",__FILE__,__LINE__);
perror("Can't open FromDH");
exit(errno);
}
and no error was caught. errno stayed 0.
still puzzled.....
thanks!
Bug
